Visibly indicating piezo electric crystal resonator



Nov, 3, 1931. 'H. EBERHARD 1,830,532

VISIBLY INDICATING PIEZO ELECTRIC CRYSTAL RESONATOR Filed Aug. 31, 1927 W ma Patented Nov. 3, 1931 PATENT OFFICE 'HEINRTCH EBERHARD, OF BERLIN-FRIEDENAU, GERMANY vIsIn Y INDICATING rnzzo ELECTRIC CRYSTAL RESONATOR Applicationfiled August 31, 1927, Serial No.

i The invention relates to a method for makalso if the electro-magnetic field is arranged in a certainmanner with reference to the direction of the crystallo-graph1c axes.

Various methods are known'for examlning and observing such'oscillations of a crystal. If, for instance, the crystal is brought into a sufficiently powerful field, microscopically small sparks may, by favourable arrangements, be caused to appear on the surface of the crystal if the conductive coatings which determine the disposition of the field (electrodes) are brought into the immediate proximity of the crystal. This method suifers, however, from the disadvantage that the crystal will easily break as soon as the sparks exceed a certain strength and the tension has becometoo strong. It has also been suggested that the crystal itself should be arranged in an evacuated or gas-filled vessel. In this manner the oscillation of the crystal may be observed by reason of the luminousiphenomena that arise.

This method is, however, suitable only if one and the. same crystal always remains sealed within the same glass vessel, because with a change of the crystal or a change of the glass vessel the test becomes cumbersome and tedious. This method also has hitherto involved great waste of time in the adjusting of the crystal since, before it was finally sealed'in the glass vessel it had previously to be reground, by way of trial, a number oftimes and to be sealed each time into the glass vessel, before it is of the desired form and dimensions.

I have found that a piezo-electrically act- 216,675, and in Germany September 2, 1926.

ing crystal does not only exhibit luminous phenomena in an evacuated vessel or vessel filled with gas, more particularly rare gas, if the crystal itself is arranged in the vessel, but that such luminous phenomena will also occur if the crystal is situated beside the vessel (i. e. outside the vessel). In that case the luminous phenomena occur only in the neighbourhood of the crystal and may be clearly distinguished from the well known flashing up of a helium tube on its entry into i a very powerful, high frequency electric field. The luminous phenomena which form the subject of my invention, will not only occur if the vessel is filled with helium, but also if it is filled with other gases, more particularly rare gases such as neon or argon. They occur, moreover, only with those frequencies in which resonance exists between anatural oscillation of the crystal and the ef- 'ffiective oscillation of the electro-magnetic eld.

The phenomenon described may according to the object of my invention be employed inorder in an electro-magnetic field to eX- cite the luminescence of a crystal whose piezoelectric natural oscillation is to be examined. By observing whether with a stated frequency (to be considered as standard frequency) the luminous phenomenon will 00- cur, I am able to ascertain whether the crys tal already possesses the desired natural oscillation and if necessary, to regrind the crystal accordingly. With variable frequency of the electromagnetic field we may also ascertain the difference between the standard frequency and that frequency at which the luminous phenomenon may be best seen at the crystal in order from the amount of frequency difference to obtain a measure of the extent to which the crystal should yet be reground. With an apparatus according to the invention these observations may be very easily carried out because according to the invention the crystal is situated outside the gas-filled vessel, the observation of the crystal with such apparatus being therefore also suited for those cases in which the crystal has to be adjusted if after the adjustment it is to be arranged in a closed (sealed) glass vessel.

The same apparatus may, if the crystal is employed as standard crystal, be used to ascertain the frequency of a transmitter producing highfrequency oscillations and to control the constancy of the frequency. For this purpose I have to observe whether a crystal in the apparatus according to the invention flashes up if the apparatus is fed with the frequency concerned.

If it is not a question of maintaining a transmitter for high frequency oscillations at a certain frequency, but of ascertaining the unknown frequency of a high frequency oscillation, several standard crystals of various known frequencies are arranged in the apparatus according to the invention.

' Thus, for instance, a number of quartz-pieces may be used which have as natural oscillations the wavelength 100, 125, 150 up to, say, 500 metres. If the apparatus is fed with the frequency to be ascertained, that quartz crystal will flash up which possesses the natural oscillation corresponding to the wavelength. With such apparatus according to the invention already froma distance may be recognized the length of the wave transmitted by observing whether the crystal piece flashing up is situated lower or higher-in a similar manner as with a wellknown frequency meter the level of the oscillating reed serves as a measure for the frequency of the oscillation.

- For the purpose, of adjusting a quartz crystal by means of the apparatus according to the invention it may in certain circum stances be found troublesome that it is not always an easy matter to keep the frequency produced by a transmitter entirely constant, whilst the constancy of a quartz resonator is a very good one. The adjustment of a crystal by means of the apparatus according to my invention may therefore be effected in such a manner that I do not employ a standard frequency but another crystal which serves as standard crystal when the frequencies of the transmitter may alternately be adjusted thus that consecutively the standard crystal and a'crystal to be adjusted will flash up. The crystalis properly adjusted if it flashes up at the same frequency at which the standard crystal flashes up. With this adjustment process it is not necessary to ascertain whether the transmitter itself is frequency-constant. v

In all these instances it is of considerable advantage if the crystal according to my invention is arranged outside the gas-filled glass vessel and as far as possible in close proximity to the same.

In order that my'invention may be best understood I have in the accompanying drawings illustrated by way of example an embodiment of the apparatus according to the invention:

Fig. 1 shows the connection of an apparatus by means of which the piezo-electrlcal oscillations may be made visible according to the invention.

Fig. 2 shows the glass vessel employed in connection with it on a somewhat larger scale.

Fig. 3 shows somewhat modified embodiment of such a glass vessel.

In Fig. 1 1 represents the glass vessel which ismore plainly shown in Fi 2. It contains two electrodes 2 which lea a high frequency magnetic field. For this purpose the two electrodes 2 are connected with a coil 3, outside the lass vessel (tube). The coil 3 is coupled in uctively across the coil 4 coupled with a transmitter 5 generating high frequency. oscillations. 6 shows tuning means, e. g. a variometer for varying the frequency of the transmitter. In the case of a variation of this tuning means 6 a value measuring the frequency enerated, for instance, the wavelength of t e oscillation produced, may be read off a dial 7. The vessel 1 is filled with a. rare gas such as neon and between the two electrodes 2 has a cylindri cally shaped cavity 8. This cavity holds a number of quartz crystals 9 all of which are ground inthe shape of a rectangle. The quartz pieces 9 are separated from one another by small pieces of non-crystalline material, for example glass tubes 10 so that they cannot mutually influence each other by their piezo-electrically excited oscillations.

Fig.. 3 shows a somewhat differentl constructed tube 1 of transparent, insu atin non-crystalline material such as glass whic for example, is filled with diluted heliumneon-gas and the inside of which contains only one electrode 2'. On the flat surface or side 8 a crystal 9 is placed. Above such crystal is shown the second electrode 2" made of a copper Wire.

The invention is not restricted to the illustrated embodiment of the tube. Thus, for example, further electrodes may be provided in order to control further circuits by the electric processes in the inside of the tube.

7 What I claim is:

1. In an apparatus for making visible piezo-electrical resonance oscillations of a crystal :1 gas-filled vessel, a crystal arranged near said vessel but outside its walls, electrodes arranged inside said gas-filled vessel and provided for applying to said crystal the electromagnetic oscillations which are required to excite the oscillations of said cryscrystal agas-filled vessel, several cr stals arranged near said vessel but outsi e its 'Walls, electrodes arranged inside said gasfilled vessel and provid for applying to said crystals the electromagnetic oscillations which are required to excite the oscillations of said crystals.

3. In an apparatus for making visible the piezo-electrical resonance-oscillations of a crystal a gas-filled tube with a cylindrically shaped cavity, several crystals arranged in this cavity of said tube, electrodes arranged inside said gas-filled tube and provided for applying to said crystals the electromagnetic oscillations which are required to excite the oscillations of said crystals.

4. In an apparatus for making visible the piezo-electrical resonance-oscillations of a crystal a gas-filled tube with a cylindrically shaped cavity, several crystals arranged in this cavity of said tube, pieces of non-crystalline material interposed between the crystals lying one upon another, electrodes arranged inside said gas-filled tube and pro vided for applying to said crystals the electromagnetic oscillations of said crystals.

5. In an apparatus for making visible the piezo-electrical resonance-oscillations of a crystal a tube with a cylindrically shaped cavity and filled with diluted helium-neon gas, several crystals arranged in this cavity of said tube, two electrodes arran ed inside said gas-filled tube and provided or applying to said crystals the electromagnetic oscillations which are required to excite the oscillations of said crystals.

7 In testimony whereof I have aflixed my signature.

HEINRICH EBERHARD. 

